Aircraft and industrial gas turbine engines include a combustor in which fuel is burned to input heat to the engine cycle. Typical combustors incorporate one or more fuel injectors whose function is to introduce liquid or gaseous fuel into an air flow stream so that it can atomize and burn. Gas turbine engines may operate using one or several types or combinations of fuel, such as propane, ethane, hydrogen, or jet fuel.
Fuel nozzles, as part of fuel injector assemblies in combustors, have been developed to operate in staged combustors with low pollution, high efficiency, low cost, high engine output, and good engine operability. In a staged combustor, the fuel nozzles of the combustor are operable to selectively inject fuel through two or more discrete stages, each stage being defined by individual fuel flow paths within the fuel nozzle. For example, the fuel nozzle may include a pilot stage that operates continuously and a main stage that only operates at higher engine power levels. Additionally, a fuel nozzle will have one or several features for mixing air and fuel before ignition.
Operating combustors with relatively high reactivity fuels (e.g. propane, ethane, or hydrogen) are limited by issues such as auto-ignition, flashback, and flame-holding. While preventing or eliminating such issues, the need exists for delivering high fuel-air premixing to the combustor for good combustion performance and engine operability across all engine loads.